Paint Viscosity Chart / Cross-reference of Ford cups to Zahn cups

A discussion started in
2003 but continuing through 2018

(2003)

Q. I am looking for a paint viscosity chart that will give me relative comparisons between a#2 EZ Zahn cup, a #3 EZ Zahn cup, and a #4 Ford cup, with the ideal temperature of the paint being 77 degrees. I have been unsuccessful in my attempts to locate a chart using the resources I have available to me. Any direction would be greatly appreciated.

Q. Many times I find it difficult to convert various viscosity parameters mainly between, Ford cup, Din cup, Iwata cup etc. Can anyone help me to find out an conversion chart between various measuring cups of viscosity.

SUBIR SIL- Shanghai, Shanghai and PRC

(2005)

A. Not very difficult, really. I just googled "viscosity conversion chart" and got 489,000 hits. The very first one on the list =>
has a comprehensive conversion chart available for free download at a click of the mouse button. No doubt there are many others among the 489,000.

www.visco.co.za/downloads/ford-conversion-chart.pdf appears to be a dead link. Any recent links referring to the same problem of converting FC - 4 data to poise?

PC Sarkar- Ranchi, Jharkhand, India

July 31, 2012

viscositycup.com/ViscosityCupConversionChart.pdf

Atul Mishra- Anjar, Gujarat, India

---- Ed. note: That one is broken now as well, but both the table offered by Bill Reynolds and the one offered by Meghan Manjrekar give you that comparison. And http://spraygunworld.com/Information2/Viscosity.html has a number of such conversion charts.

September 22, 2008

Q. I want viscosity chart for different temperatures in B4 Cup.

Mohan Subramaniyampaint industry - India

A. Hi, Mohan.

The B4 cup offers you an estimate of the absolute viscosity of a liquid in centistokes based on its efflux time. The viscosities of liquids decrease with increasing temperature. But regardless of whether you specify the viscosity in terms of centistokes or B4 efflux time or anything else, I think you would need to specify exactly what liquid you are speaking of before anyone could offer a chart to show the relationship between its viscosity and its temperature because different materials react so differently to temperature (when honey is hot it runs almost like water; when it's cold it's very thick). Good luck.

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

February 6, 2009

Q. Dear Meghan,

Do you have conversion of 552.317 cst to Ford cup B4 - secs.

Regards,

Aniruddha Oak- Bangalore, India

A. Hi, Aniruddha.

I think the problem is that that viscosity is beyond the range of proper measurement with an F4 cup. According to the previously referenced chart at www.visco.co.za/downloads/ford-conversion-chart.pdf, it looks like the efflux time for an F5 cup would be about 48 seconds.

Q. I find that Two cups - B4 cups never give the same results. Can any one explain to me the reasons? I can verify the volume of cup and the dia of orifice. Can you correlate these parameters to the disagreement of the cups? How do I say that a particular B4 cup is faulty and should be discarded?

A. Dear David and other friends,
Try www.viscosity.com -- Viscosity conversion tables by Norcross Corporation. I think it has wide range of useful information.

Sushil Samvatsar- Aurangabad, Maharashtra, India

---- Ed. note: Although you can buy a "certified" Ford B4 cup =>
I'm not sure that that really answers Sushil's question. If anyone can help, please do.

August 31, 2009

Q. Sir We are using ford cup B4. Our material is viscous. We are checking its time to empty the cup in seconds. Please send us how to convert it in to centipoise.

With Regards

Manikantan Rajanexecutive - Ambernath, Maharastra, India

August 31, 2009

A. Hi, Manikantan. Can you clarify in what way Meghan Manjrekar's chart does not answer your question? Thanks.

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

September 1, 2009

Q. Dear sir,

Sorry Sir I can't get the answer to the question from the chart of Mr. Meghan. My question was when the seconds is more than 200 sec how the conversion table will help. Please send me the conversion formula from seconds to centipoise at room temperature.

A. Hi again Manikantan. Method ASTM D1200 [link by ed. to spec at TechStreet] covers viscosity measurement with the Ford Cup. Please also try to also get hold of the ASTM Gardner/Sward "Paint Testing Manual" [link is to info about book on Amazon] as it has an excellent chapter on the subject of viscosity and its measurement with the various cups and devices. It includes a chart by Euverard showing a conversion factor of 3.7 for the Ford B4 cup. That is,

centistokes = efflux time x 3.7

centipoise = centistokes x specific gravity

But I think the problem is this: A carpenter doesn't drive tacks with his sledgehammer, nor landscape spikes with his tack hammer; he picks a different hammer for different jobs. Neither is there a single cup that allows good measurement of all possible viscosities. I think the basic problem is that you are trying to measure high viscosity liquids with the wrong cup for the job; the first step would probably be to get a cup which is designed for higher viscosity liquids than the B4 cup . . . like a B5 cup. Best of luck!

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

September 10, 2009

Q. Conversion of viscosity
We are using Dr Beck's varnish Elmotherm 97. Viscosity as per manufacturers specification is 300-400 mPa.s. We are using Ford B4 cup for checking the viscosity.of the varnish.
In how many seconds the cup should become empty. Please also specify the orifice of B4 cup. Please clarify.

V.K. ChebbiSupplier of laminated stampings - bangalore.India

December 2, 2009

Q. How to measure the viscosity in B4 ford cup? Is there any calculation available? Please clarify.

siva balanQuality Engineer - Chennai , Tamil nadu, india

December 3, 2009

A. Hi, Siva. In light of the previous answers and referenced charts & tables, I am not understanding where the difficulty lies. Can you please try to re-cast the question in terms of the answers already supplied? Sorry, I am not understanding in exactly what way the information supplied is deficient. Thanks!

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

April 8, 2011

A. As per the ASTM Method: D1200-10, "Standard Test Method for Viscosity by Ford Viscosity Cup", the following formula is used to convert efflux time in seconds (unit s) to Kinematic viscosity (unit cSt.) for Ford Cup Number 4:

Please remember that this ASTM method (D1200) covers the determination of Newtonian or near-Newtonian liquid materials. For non-Newtonian, Method ASTM D2196 [link by ed. to spec at TechStreet] should be used.

Dr. Danish Jamal- Pune, India

June 25, 2011

Q. From where do you all getting the factor 3.7 please tell me for the problem of manikantan.

Amit Patilstudent - Maharastra

June 2011

A. Hi, Amit. Unfortunately my copy of the book I quoted is out on loan so I can't double-check but, as I recall, "3.7" is simply an empirical factor that is reasonably close for a narrow range of efflux times. If you look at the previously referenced chart at www.visco.co.za/downloads/ford-conversion-chart.pdf, you will be able to see that the centistokes is reasonably close to 3.7 times the B4 efflux time in seconds.

The ASTM D1200 formula quoted by Dr. Jamal is presumably more accurate.

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

October 15, 2011

Sir, I want the conversion of Ford cup B4 unit in second to poise.
So please tell me how can I convert this.

Pravin K.student - Gujrat, India

March 3, 2013

Q. Can I measure viscosity 120-130 in B4 Ford cup?

Shah j.r.- Vadodara, India

March 5, 2013

A. Hi Shah. I can't tell whether there is something here which is specifically confusing you, or whether you haven't read the page :-)
Please explain what it is about Meghan's chart that you are not following . . . then we will be able to clarify it. Thanks!

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

Conversion of B4 cup to Zahn cup #2

July 30, 2013

Q. I would like to compare the results of my paint with other lab for NATA.
The other lab has used B4 cup using our paint and our lab has used Zahn cup #2 for viscosity testing.
Therefore I would like to see if my instrument is giving the correct reading with other lab.
Basically I am doing the Inter-laboratory testing.

So what is the relation or conversion factor from B4 cup to Zahn cup #2?

Dinesh Chandra- Brisbane, Qld Australia

July 31, 2013

A. Hi Dinesh. Why is Meghan's chart insufficient for you? Please detail the issue! I am not understanding this continual repetition of a question that I thought was already very clearly answered. Please clarify. Thanks!

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

August 4, 2013

Q.
All I need is the conversion chart or any similar that would enable my Zahn cup is giving us the true reading as B4 cup.
The B4 cup measured from other lab is made of Brass.

A. Hi Dinesh. As noted, Meghan Manjrekar has already posted the relationship between Zahn #2 Cup and Ford B4 cup on this page so you can compare your Zahn readings vs. the Ford B4 readings and decide if they are close enough. To me they don't seem to be close enough because for sample A the Zahn reading was lower that the Ford reading, which goes against the whole direction of the chart.

To my knowledge, the only B4 cup is the Ford B4 cup, but I think you can't resolve this unclear communication by asking a 3rd party what the other party was thinking :-) Good luck.

Regards,

Ted Mooney, P.E.finishing.comPine Beach, New Jersey

January 28, 2016

Q. Hello all,
As my project work I am designing an impeller for a mixing tank for solvent based paint having viscosity 100 to 140 sec (ford cup 4).
What will be equivalent viscosity in Cps?

Thank you

Ruchir Patel- dortmund,NRW,Germany

January 2016

A. Hi Ruchir. Although I am not an expert on this stuff, I am pretty confident from simply reading this page, and looking at the several conversion charts on it, that your problem is the same as Aniruddha's previously explained situation, i.e., that you have a cup that is designed to measure low viscosity fluids, and you are trying to use it to determine the viscosity of a high viscosity fluid.

You're not finding the conversion factor that you're looking for because people DON'T WANT YOU TO EXTRAPOLATE SO FAR BEYOND THE VISCOSITY RANGE THAT A FORD B4 CUP IS DESIGNED TO MEASURE. The charts tell you the viscosity of fluids that drain in 5-60 seconds, probably most accurately when the drain time is 15-30 seconds. But what is the viscosity of a fluid that takes 140 seconds to drain from a Ford B4? Well, the chart makers don't want us to hazard such wild and unrepeatable guesses … they want you to please get yourself a cup with a bigger hole :-)

A. Paint viscosity is not a simple subject. Most paints are deliberately formulated to have non Newtonian characteristics. i.e. they typically contain thixotropic agents which give non drip properties. The flow rate (viscosity) depends on the shear speed so that the paint goes on thin and does not immediately flow off again before the solvent evaporates.
Ford, Zahn and similar measures are simple devices for use in the paint shop to confirm that under a very limited set of conditions the paint is thinned to a degree suitable for spraying. They are only comparators.
If you need a more accurate assessment you could start with
http://www.brookfieldengineering.com/download/files/Paint_Viscosity_Temperature.pdf
Welcome to the world of Rheology.

Geoff Smith Hampshire, England

May 31, 2017

A. From literature, I find that the kinematic viscosity (cSt) tapers off with increasing flow times in Ford cups or Zahn cups, above 40 - 60 secs flow times. So, it does not make much sense to measure flow times that exceed 60 secs, and try to correlate to cSt / cPs.

Mohan DasPolymer Consultant - Bangalore, Karnataka, India

May 22, 2018

Q. Kindly clarify conversion unit for viscosity from cst to KU unit.

PURUSHOTHAMAN Devaraj- Trichy,India

May 2018

A. Hi Purushothaman. There is a 2-step conversion process presented at https://www.gardco.com/stormer_krebsconv_PU-G271.pdf
… first you convert Krebs Units to centipoise from a graph they offer you, then you convert centipoise to centistokes by dividing by the specific gravity (S.G.) of your liquid.
You can work it in reverse by multiplying your centistoke value by the S.G. to obtain centipoise, then look on the graph for the corresponding Krebs Units value.
As that page will warn you, and this page already warns you, such conversions are only accurate for newtonian and near-newtonian fluids (where shear force is directly proportional to speed) and within limited ranges. Good luck.

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